Street 350 Small Block - Cam Comparison

Flat-Tappet Or Roller Cam? We Build A Budget Street 350 To Put Them To The Test.

It's often said that money makes the world go around. And it's true to some extent. Our hobby is often ruled by the almighty dollar. We crave a set of three-piece forged wheels, but our wallet steers us toward budget-friendly cast wheels. We shop for the best deal and agonize about the price, but can we go too far? This happens with engine builds all the time. To save a couple of hundred bucks, we stuff in cast pistons, only to regret the decision when we get the itch to strap on a nitrous system. We lose the bottom end of our engine because a factory bolt failed when a set of high-end bolts would have cost us under $50. Sure, we should be frugal with our hard-earned cash, but it's not really a savings if it costs you a lot more down the line.

For this story we wanted to build your typical 350 small-block, an engine as iconic to our hobby as Rolex is to watches. The idea was to put it together the way your average gearhead would. Spend cash where it made sense and try to save a buck when it wouldn't cause problems later on.

The biggest choice involved the valvetrain. Solid cams are great for big power and race cars, but if you plan on logging tons of miles, adjusting valve lash can get old. Hydraulic flat-tappet cams are pretty much maintenance free and very economical, but oiling issues can flatten out a lobe in the blink of an eye. Hydraulic roller cams are what all the new engines run, but they can be pricey. Or are they? Sure, they cost more compared to flat-tappet equivalents, but if you're spending three to four grand on a new mill, is another $500 going to put you in hock? If your cam goes flat, any savings you enjoyed by going flat tappet will evaporate. The hydraulic roller arrangement is more reliable, and you won't be screwed if you forget to pour in a bottle of additive when you change your oil like you would be with a flat-tappet setup.

To test this out, we built a middle-of-the-road 350, dynoed it with a flat-tappet cam, and tossed in a hydraulic roller cam to see what would happen.

The heart of our build is this crank. According to eagle, its ESP cast steel crankshafts have a higher ductility than OE units and feature .092-inch radii on all journals for added strength. They can also use OE-style bearings. Brian Taube of Eagle Specialty Products told us this package is rated for 500 hp at 6,500 rpm. Eagle also treated the crank, rods, and piston tops with its new ESP Armor finishing process. This process results in a more durable surface and stronger parts, and the slick surface sheds oil better.

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Eagle can balance the entire rotating assembly on its Hines equipment. This saved us the hassle of having it done locally and let us get to the assembly stage that much faster. Eagle also sent us the properly weighed flywheel. Eagle is known for high-quality connecting rods, and these forge 6.000-inch 5130 SIR I-bean units are no exception. They're bushed to work with full-floating piston pins. The rods also utilize ARP cap screw fasteners and have alignment sleeves for easier assembly. They forged pistons are Mahle slugs and come coated right out of the box. The choice to run forged pistons means we're good to go if we want to toss on a 125 shot of nitrous for the track.

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At first we tried to find an early 350 block for our build, but everything we found was either too expensive or too worn out. After speaking with the guys over at AA Midwest, we found that we're not the only ones having this problem since they are seeing fewer and fewer nice early blocks as well. They suggested a later-model block, in this case from 1986. They are plentiful, in excellent condition, and can be had for a decent price. This four-bolt main block set us back $250 and included the seal retainer needed for the later one-piece main seal blocks. AA Midwest also offers an adapter so you can run a two-piece seal crank in a newer block. Here you can see the block after we cleaned it and had it rough-honed.

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Now it was time to turn our short-block into a full-fledged engine. First up was bolting on the Racing Head Service (RHS) aluminum 180 heads (PN 12022-0, $747 each). These Pro-Action 23-degree heads feature a 64cc chamber and come fully assembled. RHS advertises that the peak airflow at .700-inch lift is 270 cfm on the intake and 195 cfm on the exhaust. If you need to save a few bucks and don't mind the extra weight, RHS also offers these heads in an iron version (PN 12317-01, $561.38 each). For head bolts we went with a kit from ARP (PN 134-3601, $61.95). At that price, why wouldn't we?

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For an ignition system, we went with MSD's new Street Fire billet HEI distributor (PN 8362, $159.99) and matching plug wires. Since the wires were only $40, it meant our entire ignition system came in at only $200. It's hard to argue with MSD quality at such a wallet-friendly price. Topping off our Weiand intake is Holley's new 650hp street-version carb. To keep things running cool and knock off some weight, we also sourced Weiand for one of its aluminum water pumps. We started this build with a bare block and didn't have any fasteners. Rather than hunt around for all the various intake, water pump, header, and other bolts, we just picked up an accessory bolt kit from ARP (PN 534-9801, $79.95). This saved us a ton of hassles, and as a bonus, they look great. Other parts used in the build came from Summit and include the water neck (PN SUM-G1581, $13.95), distributor clamp (PN SUM-400500, $4.95), and these sweet chromed valve covers (PN HLY-241-80, $57.69).

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In addition to the roller cam, we installed a set of comp roller lifters and the necessary retention kit. Since our '86 block was already set for roller parts, the swap was a snap. We also needed to change to a shorter 7.200 pushrod, but we were able to use the same rockers. Steve Brule of Westech Performance Group also installed the stiffer springs that come on the RHS heads if we would have ordered them for a roller application (PN 1-2022-02, $803.25 each).

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With the much smaller and more street-friendly hydraulic roller cam, our 350 put down 387 hp and 416 lb-ft of torque than the lumpier flat-tappet cam. More importantly, the roller cam has much better street manners, with over 17 inches of vacuum at 1,000 rpm compared to under 11 inches on the flat-tappet engine. This equates to an improved idle quality and a more reliable engine for a ride that sees lots of street time. We will also never have to worry about the roller cam going flat. The downside is cost $500 more to go the roller route, with a lot of that being spent on the lifters. Still, the total cost of our engine with the roller cam was an affordable $4,200.